An electronic amplifier is a device for increasing the power of a signal. Generally, an amplifier outputs energy from a provided power supply and controls the output to match an associated shape of an input signal with a larger amplitude. There are many types of electronic amplifiers, and they are commonly used in radio and television transmitters and receivers, high-fidelity stereo equipment, microcomputers and other electronic digital equipment, and audio amplifiers. Digital waveforms commonly used in high-definition (HD) television and radio broadcast and wireless carriers employ deep amplitude modulations of the RF signal. The RF signal will go from very low levels (and very low efficiency) to very high levels (and high efficiency). Over the last century, several techniques have been devised with the purpose to maintain high efficiency at lower levels of the RF signal. For the most parts these techniques fall into one of three categories; impedance modulation, drain modulation, and switched mode amplification.